Internet acces via cable TV network by Florian Gnägi 
 
Content: 
 
Where to go:
Introduction
56k modem
ISDN
ADSL
cable TV
power
satelit
home of the seminar
 
Introduction: 
For many kind of teleworking it is important to have a permanent computer connection to your company. For example this may be true when you have to work with client server applications or databases running on the host at the company. 
To establish a permanent connection we can use xDSL-connections, but in most cases this would be too expensive. As an alternative to the copper wire we can now use the coax cable of the cable TV providers to have a permanent connection with Internet. But unlike the xDSL method it is not possible to have a private connection to the company with this technology - we share the cable with other participants of this service.  
 
 
Preconditions: 
 
  • Permanent connection is recommended

    • An Internet connection over coax cable is ingenious if it is important to have a permanent connection to your company. The reasons therefor are many-sided. It is important to know, that with this technology no specific bandwidth is guaranteed. Like in the real Internet you have to share the connection with the other participants. Whenever you need a permanent connection and a guaranteed bandwidth at anytime you may not choose the cable TV network a your connection to your company. 
     
  • You and your company have got the same cable TV provider

    • Since you have got a connection to the real Internet with this technology, it might not be necessary that your company has an access to the same cable TV provider as you. But ifit has, it will increase the speed of the connection significantly, because the cable TV network runs much faster than the connection from the cable TV network to the backbone. This bottleneck will disappear in the long term, but in the near future this might be a problem. 
     
  • Your cable TV provider is also Internet provider

    • Not all cable TV provider are planning to become Internet provider yet. Actually this very new service is limited to some pilots in specific test areas, but this will change in the foreseeable future. Since all the pilots where positive, the providers start now with the implementation  over their whole network. The "Antennengenossenschaft Dattenberg, Kriens" for example provides this service already on the entire network, while the "cablecom" in Zurich just finished with the pilots. 
     
  • You need a computer with either a free socket for a LAN card or an Ethernet connection

    • There are two possibilities to connect the computer to the modem: you plug a modem card into your LAN socket in the computer, or you connect the modem and your computer via Ethernet. The modem is working without any drivers - it already understands TCP/IP. There is no specific computer system supported or not supported. It works with everything that can communicate via TCP/IP. 
     
  • You need a specific cable modem

    • There exist many different products on the market and there is no standard yet. The performance of the different modems is varying very much. Normally you will get the right modem directly from your cable TV provider. In most cases, you can rent or buy the modem. 
     
Technical:
 

Cable TV networks are one way broadcast networks, based on coax cable. We distinguish between the download and the upload band-width. Today the following frequencies can be used: 

  • download: 47-450 MHz
  • upload: 5-30 MHz
In the future the  so called "Full Service Networks" will increase the band-width: 
  • download: 47/80-862 MHz
  • upload: 5-30/65 MHz
The today existing cable TV networks usually do not dispose a backward channel.  To use the cable TV networks as a door to Internet, this feature has to be implemented first. Since the band-width of the backward channel is limited and may not be big enough in a big network island, the cable TV provider has to grow up the capacity of the backward channel from some distribution centers to the main network via xDSL connections or other added connections. In most cases, this connections do not exist yet and they have to be built up first. These are the reasons, why this new service is coming up step by step from region to region. 

With this cable modem technology we can reach speed up to 36MBit/s. The real installed modems will allow us maximal download rates between 2 and 4MBit/s. On the backward channel upload rates between 64kBit/s and 10MBit/s are theoretically possible. In the practice these values are depending on the used modems. At present most modems allow down streams up to 3MBit/s and up streams between 100 and 800kBit/s. The "Home Works Universal" made by Zenith as a special case can work with 4MBit/s in both directions (duplex). 
 
 
Advantage:
 
  • High availability

    • Many households in Europe are equipped with cable TV. Germany for example has more than 17 millions cable TV participants and in Switzerland there are about 2.5 millions. All these households could theoretically be connected to  Internet via such a cable TV connection. Today, only in a few regions one can use this technology, but in the foreseeable future all cable TV provider will also provide this service. 
     
  • High band-width to low costs

    • Although a specific band-width can not be guaranteed, the costs of such an Internet connection is extraordinary cheap. It is to early to make any statements about the performances. The question is,  how fast will it be when everybody is using it? 
     
  • Permanent connection to low costs

    • No other technology gives you the advantage of a permanent connection to  Internet to such low costs. Only shared xDSL connection can reach the same price level. 
     
  • The costs are independent from time usage and data volumes

    • Since it is a permanent connection, time using Internet makes no difference to the calculation of the costs. Most cable TV provider have got a global price per month, independent from the uploaded and downloaded data volume. Some use a price model based on the caused traffic. 
     
  • The phone line is not busy

    • You are able to work and surf in Internet and making a phonecall at the same time. The phone line is never needed. In the future, it will be possible to make phonecalls directly over the cable TV network. 
     
Disadvantage:
  • The security of datas is not guaranteed

    • There is one stream of datas comming up through the cable and your modem has to filter out the packets conearning to you. But everybody using this network can "sniff" your packets if he knows enough about the technology. Like in the real Internet, this connections are not safe. Its up to you using encryption technologies and secure servers. 
     
  • Unsafeness of a  cable TV network

    • Unlike telephone connections, the cable TV network depends onthe power. If there is a power failure, the network will be down. It is very easy to bring disturbances in the network, using simple transmitters and at least, it will happen, that the cable TV company has to shutdown the network for maintenance. 
     
  • Bandwidge  is not guarandeed

    • Since you share the TV cable with other participants, no specific bandwidge will be guaranteed. 
     
Costs:
  • Cable TV connection:

    • In your office you will normally not have a cable TV connection. First an electrician will have to install it, what can be quite expensive. 
     
  • Modem:

    • The costs for modems are between  650.- and 1500.- SFr. Usually, you will buy or rent the modem directly from your cable TV provider. 
     
  • Subscription: Example in Switzerland

    •  
    Cable TV basic: 20.- SFr. / month
     
    Cable TV Internet:
    Kriens: Subscription: 45.- SFr. / month
    Rent modem: 30.- SFr. / month
    Buy modem: 640.- SFr.
    Urbanet: Subscription (with rented modem) 99.- SFr. / month
    Cablecom: Subscription: 65.- SFr. / month
    Buy modem: 790 .- SFr.
     
     
Summary:
Internet access via cable TV network is interesting in many point of view: it is fast, cheap, easy to install and use and you have the advantage of a permanent Internet connection. 
For teleworkers this is a very attractive  alternative to get Internet connectivity. If guaranteed bandwidge is important, this technology may not be the right one for you. Also the fact, that the Internet technology generally spoken seems to be unsafe, may make you decide against a connection via a cable TV network. 
 
Bibliography: